Field of the Invention
The present invention relates to a measurement apparatus, a lithography apparatus, and a method of manufacturing an article.
Description of the Related Art
As semiconductor devices become finer and are integrated at a higher density, higher performance is requested of a lithography apparatus (for example, an exposure apparatus) used to manufacture such semiconductor devices. For example, the precision of alignment between a reticle (mask) and a substrate is important as the performance of the exposure apparatus, and there is a demand for a technique of aligning the image of the pattern of a reticle with a pattern formed on a substrate in the nanometer order.
The exposure apparatus sequentially transfers the pattern of a reticle to shot regions of a substrate with the intervention of step movement of the substrate. Exposure apparatuses of this type are classified into a so-called stepper that performs the transfer at once, and a so-called scanner that performs the transfer while scanning a substrate.
As disclosed in Japanese Patent Laid-Open No. 2004-235354, alignment of a reticle (also called reticle alignment) with respect to a reticle stage can be performed by detecting a reticle mark provided on the lower surface of the reticle and a reference mark provided on the upper surface of the reticle stage. Accordingly, for example, the misalignment amount of the reticle with respect to the reticle stage can be measured. When transferring the pattern of the reticle to the substrate, at least one of the position of the reticle stage and the position of the substrate stage can be corrected to perform alignment between the pattern image of the reticle and the substrate with a high precision.
When a particle (dust) is attached to the reticle mark or the reference mark, or a defect such as a scratch exists, the position of the mark may be erroneously measured. In such a case, reticle alignment processing is stopped as an error. However, if the processing is stopped even in a case in which a measurement error arising from a particle or a scratch is negligible in terms of precision when processing substrates with various overlay required precisions, the throughput of the exposure apparatus (measurement apparatus) is decreased.